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Math Help - Newton-Raphson method

  1. #1
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    Newton-Raphson method

    An equation f(x) = 0 has two roots in the interval between 0 and 8.
    Give the value or a description of two starting values for which the newton raphson method will fail to converge to either root of the equation.

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  2. #2
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    Quote Originally Posted by sillylilly View Post
    An equation f(x) = 0 has two roots in the interval between 0 and 8.
    Give the value or a description of two starting values for which the newton raphson method will fail to converge to either root of the equation.

    cheers
    Read practical considerations here: Newton's method - Wikipedia, the free encyclopedia
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    Yes I was just reading that before, only I don't understand how I can relate that directly to my problem?
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  4. #4
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    If f(x)= 0 has two roots, then, by Rolle's theorem, there exist a value of x between those roots at which f' is 0. Quoting from the Wikipedia article mr. fantastic linked to
    "4. It is clear from the formula for Newton's method that it will fail in cases where the derivative is zero. Similarly, when the derivative is close to zero, the tangent line is nearly horizontal and hence may "shoot" wildly past the desired root."
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